Air propeller with automatically variable pitch



Get. 24, 1939. u, DE c R 2,177,315

AIR PROPELLER WITH AUTOMATICALLY VARIABLE PITCH Filed Aug. 17, 1937 2 Sheets-Sheet l INVENTOR/ 7/ 0 De (I?! '11? BY g 3 7 2TORNEYS.

Oct. 24, 1939. u. DE CARIA 2,111,315

AIR PROPELLER WITH AUTOMATICALLY VARIABLE PITCH Filed Aug. 1'7, 1957 2 Sheets-Sheet 2 INVENTOR/ Patented Oct. 24, 1939 Am PROlELLEB. wrrn AUTOMATICALLY I VARIABLE rrrcn Ugo De Carla, Milan, Italy Application 3 Claims.

The present invention relates to propellers wherein the pitch of the blades is automatically varied andthe invention more particularly pertains to means for limiting theaxial rotation of the blades of such propellers.

My copending patent application, Serial No. 52,240, filed November 29, 1935, relates to Air propeller with automatically variable pitch, and

provides some mechanical arrangements adapted ior automatically varying the pitch of propeller lades.

August 17, 1937, Serial N0.159,556 In Italy April 23, 1937 In carrying the invention into practice "prefer-.

ence has been given to the arrangement. ofFigures 1, 2 and 3 of the drawings annexed to the above mentioned 'copending application with modifications and improvements specified hereinafter.

In the first place, for the mechanism formed by the arms e, connecting rods 1 and arms g, as shown in the three figures above referred to, a coupling device has been substituted comprising conical toothed wheels suggested in the above mentioned copending application, as an alternative embodiment of the invention. Moreover stops limiting the extreme values-of the pitch are interposed between the hub b and the shaft a and more precisely between two discs applied to said members. The shock which could occur againstthese stops-during the rapid variations of the angular speed of the propeller is damped by suitable resilient members.

In practice no necessity has been felt for damping devices according to the above mentioned application which tend to render the variations of pitch smoother. A noticeable improvement, however, has been created by providing that the automatic variation of pitch occurs only at speeds used in practice, so as to avoid or reduce changes in the pitch of the blades .on starting of the en:- gine and during operation at minimum speeds. Starting of the engine often occurs suddenly, while the operation at a minimum speed is often irregular, thus producing in the absence of suitablefdevices, excessive shocks against the stops. .Such desirable features, have been realized by means of friction means interposed between the propeller. bearing shaft and the'hub, this friction being increased by means of springs and released by' centrifugal masses, so as to render the pro-' vention is shown in the annexed drawings, wherein Fig. 1 shows the propeller partly in side elevaticn, and partly in longitudinal section.

Fig. 2 shows the propeller in a plan view.

Fig. 3 is a view, partly in cross section, show.- ing the stopping device at the end of the stroke.

In the drawings:

a is a sleeve rigidly keyed to the propeller carrying shaft; b is the hub of the propeller, which is free to rotate on the sleeve a but retained thereon against axial movement; 0 are the blades of the propeller, two of which are shown, but any number may be employed. These blades 0 are connected with the hub bin such a manner as to be ableto rotate about their geometrical axis thus varying the pitch angle.

0n the blades 0 are keyed masses d in such a manner that, owing to the component F of centrifugal forcewhich develops during the rotation of the propeller, they tend to rotate the blades in such a manner as to increase the pitch. Moreover the blades carry gear sectors e which mesh with a conical pinion gcohnected to the sleeve a.

- consequently between the discs i and h.- This rotation is limited by. the projections l and m and by the resilient blocks n, and as a result the variation of pitch will be limited.

Friction means is also interposed between the discs h and i. Precisely, the disc 1' is provided with an annular projection 0 having grooves.

On-these grooves slides the friction disc p pro;- vided with a lining q. The disc '12 is pressed against the disc h, by a number of screwbolts T which, in their turn, are kept screwed up by the coil springs s which tend to thread said screw- 'bolts r into threaded holes provided in the dlscfl. r

The action of said-springs s is opposed by the centrifugal force acting on suitable counterweights t tending to rotate in such a direction as to reduce the pressure exerted by the screw-bolts r on the disc 9.

sleeve relative to the hub member,.m'eans carried.

or rotated at a low angular speed, the friction is increased by the springs s and therefore the propeller acts as a propeller having a fixed pitch. However, as soon as the angular speed has reached a suitably predetermined value the centrifugal force acting on the counter-weights t counteracts the action of the springs s, and the friction will be decreased leaving the propeller blades free for automatic movement.

The propeller blades are driven by the couple established through the pinion g meshing with the gear sectors e. After the weights 1; move outwardly to release the friction clutch between the discs the blades will assume the proper pitch angle. The driving torque acting through the pinion g tends to increase the pitch of the blades and such turning of the blades about the lon itu'dinal axes thereof is counteracted by the centrifugal force acting on the weights (1. The resilient blocks n between thezprojections I and m provide stops for limiting the angular relation between the sleeve a and the hub b and do not normally provide means through which the driving torque is transmitted.

The arrangement of the springs and counterweights may vary, without altering the operating principle. I

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that .what I claim is:

1. In a variable pitch propeller, a driving sleeve. a hub member mounted for rotation-relative to said sleeve,a propeller bladesecured in said hub member, said hub member being rotatable about the axis thereof so that the pitch of the propeller blade may be varied, a gear segment carried by said hub member, a pinion gear fixed to said sleeve meshing with said gear segment so as to decrease the pitch of the blade' during rotation of the by the blade operably responsive to the centrifugal force acting thereon for increasing th pitch of the blade during whirling of the prope e ,a disk mounted to turn with said sleeve, a second disk second disk, yieldable means for moving said frice tion means into engagement with the first disk so as to prevent relative movement between the sleeve and the hub member, and means operably responsive to the centrifugal force acting thereon during the whirling of the blade above a prede- 5 termined speed, for releasing said friction means from engagement with the first disk.

2; In a variable pitch propeller, a driving sleeve, a hub member mounted for rotation with respect to the sleeve, a propeller blade fixed to the sub member, means'associated with the hub member and the sleeve for decreasing the pitch of the blade when the driving torque of the'sleeve causes relative movement between the sleeve and the hub member, means operably responsive to the centrifugal force set up during whirling of the blade for increasing the pitch of the blade, a disk mounted tobe moved by the s1eeve,friction means 'carried by the hub member, yieldable means for moving the friction means into engagement with go said disk so as to prevent relative movement between the sleeve and the hub member, and means operably responsive to the centrifugal force act- 'ing thereon when the whirling speed of the blade reaches a predetermined value for releasing said 26 friction means for engagement 'with said disk.

3. In a variable pitch propeller, a driving sleeve,

a hub member mounted for rotation with respect to the sleeve, a propeller blade fixed to the hub member, means associated with the hub member andthe sleeve for decreasing the pitch of the blade when the driving torque of the sleeve causes relative movement between the sleeve andthe hub membenmeans operably responsive to the centrifugal force set up during whirling of the blade mounted to be moved by thesleeve, friction means carried by the hub member, a spring actuated bolt for moving the friction means into engagement tion means released from engagement with the 45 "UGO DE CARIA.

36 for increasing the pitch of the blade, a" disk 

